Dean's Mentor
by Asperitas
Summary: "I'm sorry, Sammy." Dean makes a decision that can change everything. Features the one person Dean shares the most twisted mentor/student relationship with. No slash.


**Hey! I'm back with another One-Shot for Supernatural. This one's about Alastair and Dean and is AU from 4.16 (I think, too lazy to properly look it up), which is the episode On The Head Of A Pin, where Alastair is (SPOILER ALERT) killed by Sam. Maybe you'll get a sequel, maybe you won't. If you're also reading Actually, it was quite simple, you'll be happy to hear, that I'm working on a sequel. More informations can be found in that story. Have fun with this One-Shot, and review. I don't usually do this, but:**

 **WARNING: Something like Stockholm Syndrom**

Alastair held Dean up by the collar of his shirt and punched him again and again. Dean wasn't even able to groan in pain. Alastair dropped him and grabbed him by the throat, slamming him against the wall. Dean dimly noticed that his feet no longer touched the ground.

"You got a lot to learn, boy. So I'll see you back in class bright and early Monday morning." Alastair told him with a grin. Dean's eyes widened once he spotted Castiel behind Alastair. Alastair turned and dropped Dean to the floor. Dean hissed in pain and didn't move. His entire body hurt and he coughed weakly. Castiel stabbed Alastair in the chest and the demon sparked as if he was going to die. Nothing happened. Dean's heart plummeted. He had known about this, he had stabbed Alastair with the knife before, but it still was destroying his hope to survive this.

"Well, almost. Looks like God is on my side today." Alastair mused. Then he grunted in pain and pulled out the knife, lunging at Castiel. Castiel didn't stand a chance and soon Alastair had him against the wall by his neck. "Well, like roaches, you celestials. Now, I really wish I knew how to kill you. But all I can do is send you back to heaven." Alastair said disappointed and began to chant in latin. Then he was slammed against the wall. Dean frowned and turned his head. His pain was diminishing slowly and he was capable of moving again. "Stupid pet tricks." Alastair said and Dean spotted Sam, his hand outstretched. "Who's murdering the angels? How are they doing it?"

"You think I'm gonna tell you?" Alastair asked him amused. Dean slowly moved his arms.

"Yeah, I do." Sam said confidently and twisted his hand. Dean closed his eyes in pain. What had Sam done? Alastair choked on nothing and his eyes turned white.

"How are the demons killing angels?" Sam repeated.

"I don't know." Alastair admitted.

"Right." Sam said sarcastically.

"It's not us. We're not doing it." Alastair told him again.

"I don't believe you." Sam told him.

"Lilith is not behind this. She wouldn't kill seven angels. Oh, she'd kill a hundred, a thousand." Alastair said amused and Sam stopped short. Castiel was looking between the two of them, in shock.

"Oh, go ahead. Send me back, if you can." Alastair taunted.

"I'm stronger than that now. Now I can kill." Sam stated confidently and held out his hand. Alastair slammed against the wall one last time and then he started to light up. Everything seemed to slow down. Sam's eyes were closed in concentration and Dean watched in disbelief. Alastair was going to die.

Alastair was going to die. Dean shut his eyes and everything seemed to slow down. He'd finally be free of Alastair. Alastair. His torturer. His mentor. His friend, his confidant, his torturer. Alastair screamed in pain and he opened his eyes again, suddenly completely calm. His eyes met Alastair's and the demon seemed to know what was going on in his mind. And he grinned. Dean flinched at another scream. His mentor. He let out a shaky breath and pulled himself up. He gritted his teeth at the pain, but he had endured far worse. This was nothing in comparison. He got to his feet and stumbled forward. The next step was a lot more graceful.

Alastair grinned harder.

Sam opened his eyes and frowned. Castiel watched in disbelief before he got what was going on. He was still crumpled to the floor, but he fought to stand up. "Dean, do not interfere!" he ordered in his gruff voice. Dean closed his eyes and opened them again. "Sorry." he said with a weak grin. Then he lunged at his brother.

He crashed into him and they both fell to the floor. Dean stopped a pained whimper from leaving his mouth. Sam lost the concentration necessary for killing Alastair and Alastair fell to the ground with a loud crash. The brothers quickly got to their knees and stood up again. Sam was wary and Dean was resigned.

He knew what he had to do. "What are you doing?" Sam asked angrily. Dean winced slightly. "Dean!" Sam demanded. "I'm sorry, Sammy." Dean told him with another wince of regret.

He lunged again and proved that even in his weakened state he was a better fighter than his brother. He took his brother by surprise, twisted him around by his hair and slammed Sam's face into the table, wincing at the crack from his broken nose. Sam staggered to the ground with a pained groan, momentarily disoriented.

It was enough. Dean rolled his neck and eyed Castiel warily. Castiel came closer, keeping a wary eye on Alastair. "Goodbye, Castiel." he intoned and raised his hand in Castiel's direction. He closed his eyes for a moment, searching for the words the demon he was saving had taught him a few weeks ago in earth time but a few years ago in hell time. Castiel stepped forward, anger coursing through him. "Dean, stop thi-"

Dean began to chant. Not many people, demons, knew this chant. It was powerful, that was why it was so well hidden. Angels didn't want anyone to know that the spell existed. Castiel gripped his head in pain and looked up, looking betrayed. Dean took a deep breath. "I'm sorry." he mumbled again. Then he continued. He could see Castiel straining under the spell, trying to escape it's power, but nothing happened. Then he flickered once, twice and was banished. It was another, a spoken, version of the angel banishing sigil Anna had used. He turned his gaze onto the white-eyed demon that began to laugh. Dean closed his eyes and for a moment it felt like he was back in Hell. "So much for loyalty between brothers." Alastair coughed out. He stood up with a leer. "See you soon, my apprentice." he told Dean with another twisted grin. Then he disappeared, leaving Dean with his battered body and his angry brother. "Dean, do you know what you did?!" Sam asked him angrily and held his nose. "You helped Alastair escape! Alastair!"

Dean closed his eyes again. The adrenaline slowly disappeared, leaving him weak and forcing him to feel the extent of his wounds. "I'm sorry, Sammy." he croaked. "I'm sorry."


End file.
